This invention relates to high pressure common rail fuel injection systems. Currently, such systems are used in engine testing. This invention also contemplates installation in a vehicle to provide a more clean burning engine.
Currently, the automotive industry does not have a reliable high pressure fuel system which is compatible with alcohol fuels.
Mechanically driven high pressure piston fuel pumps are typically used for high pressure diesel fuel injection systems. These type pump systems require lubrication of the moving parts by the fuel. Alcohol fuels, in comparison to diesel, have very low lubricity and reliance on an alcohol fuel for lubrication will result in premature wear of the internal pump components. Further, these pumps are expensive due to the requirement for high precision of internal pumping components.
In conventional hydraulically intensified fuel injectors, low pressure fuel enters the injector and is intensified in pressure by a hydraulic piston. The injector and intensifier are contained in a single unit, which requires separate hydraulic and fuel supplies. The disadvantage of such a fuel system is the large number of moving parts, since each injector has an intensifier piston assembly. There are also individual hydraulic lines and fittings for each injector. The large number of moving parts and individual lines increases the expense of the fuel injection system, decreases durability and the useful life, and increases the possibility of leakage.
The present invention separates the intensifier from the injector and provides a structure having fewer parts to wear and fewer hydraulic lines to potentially leak. The system has at least two intensifier units which use hydraulic fluid to pressurize fuel supplied to a common rail. These intensifiers alternately supply high pressure fuel to the common rail and refill with low pressure fuel.
Accordingly, the present invention provides a common rail intensifier fuel injection system for a multi-cylinder internal combustion engine with multiple cylinders. The fuel injection system of the present invention includes a plurality of fuel injectors respectively associated with the multiple cylinders and a common rail for supply of fuel at an intensified pressure to the plural fuel injectors. The fuel injection system further includes a fuel supply containing fuel at a low pressure, relative to the intensified pressure within the common rail, and at least two pressure intensifying circuits for alternately supply fuel at the intensified pressure to the common rail. The system further includes a source of an operating fluid which can either be hydraulic fluid or air (pneumatic). At least one of the fuel pressure intensifying circuits includes a fuel pressure intensifier having an operating chamber of a first diameter for receiving and discharging the operating fluid. The fuel pressure intensifier also has a fuel chamber of a second diameter, smaller than the first diameter, for receiving fuel at the low pressure from the fuel supply and discharging fuel at the intensified pressure to its associated fuel pressure intensifying circuit. In a preferred embodiment a double piston extends between the two chambers of the intensifier with a first piston head in the operating chamber and a second piston head in the fuel chamber. The system further includes at least a first control valve for, in a first position, connecting the operating fluid source with the operating chamber of the fuel pressure intensifier and, in a second position, connecting the operating chamber of the fuel pressure intensifier with a drain. A controller or xe2x80x9ccontrol meansxe2x80x9d is included for switching the control valve between the first and second positions and for switching the supply of fuel at the intensified pressure to the common rail between the plural fuel pressure intensifying circuits.
In one preferred embodiment the fuel injection system described above further includes an accumulator for storing fuel at the intensified pressure and a second control valve switched between at least two positions by the control means, connecting the accumulator with the common rail in one position and connecting the accumulator with the fuel pressure intensifier in another position.
In another preferred embodiment the fuel injector system of the present invention includes another fuel pressure intensifier, as described above, which provides fuel at the intensified pressure to a second fuel pressure intensifying circuit.
The fuel injection system of the present invention offers the advantage of providing the high pressure supply for a methanol fuel, which system is compatible with a hydraulic pressure power source.